Various fabrication apparatus employ weigh stations for processing relatively thin sheet material. In the context used herein, sheet material may include mailing envelopes, sheets of paper or cardstock, web material, woven fabric, composite laminates, etc. One such apparatus is a mailing machine which processes mailing envelopes (i.e., a form of sheet material) to apply postage indicia based upon mailpiece weight.
Mailing machines perform a variety of operations including feeding, folding, inserting content material, sealing, weighing, and printing (i.e., printing the address information and postage indicia on the envelope). Generally, these steps are performed sequentially, i.e., serially, by various processing stations dedicated to the particular operation. Principle among these processing steps, are the weighing of the mailpiece and the printing of postage indicia based upon the mailpiece weight. That is, since the cost of mailing has historically been based upon the weight of the mailpiece, most conventional mailing machines will minimally include a weighing and printing station to perform these functions.
The efficiency of a mailing machine is typically measured by the number of mailpieces (i.e., those of a conventional size such as number ten [10] mailing envelopes) processed per unit time. For example, modern mailing machines are typically capable of processing at an upper rate of about two-hundred and sixty (260) mailpieces per minute, depending upon the complexity of the mailpiece job run. For example, if the weight of a mailpiece is known, the requirement to weigh the mailpiece can be eliminated, hence the mailpieces can be processed rapidly, e.g., at the maximum rate of about two hundred and sixty (260) mailpieces per minute. If, however, each mailpiece must be weighed, then processing occurs more slowly, e.g., at a substantially lower rate of about one hundred and thirty (130) mailpieces per minute.
The processing speed is also impacted by the required spacing between mailpieces and ability to move one mailpiece independent of another. With respect to the spacing between mailpieces, it will be appreciated that mailpieces spaced in twelve inch (12″) increments will take longer to process than mailpieces spaced at six inch (6″) increments. While it is desirable to minimize the spacing between envelopes, the spatial relationships and size requirements imposed by the various processing stations imposes significant design limitations which tend to increase the required spacing.
For example, in FIGS. 1a and 1b, profile and plan views, respectively, are shown of a prior art mailing machine 100, including a feeding station 102, a sealing station 104, a weighing station 106 and a printing station 108. The various stations 102, 104, 106, 108 are adapted to process mailpieces 110 ranging in size from (i) a post card size sheet (3.5 inches×5 inches), (ii) conventional No. 10-type envelopes for holding standard C- or Z-folded letter-size sheets of material, and (iii) even larger flats-type envelopes for containing standard unfolded sheet material. Consequently, the deck 106D of the weighing station 106 is configured to span a length sufficient to hold both envelope types.
Furthermore, certain stations, such as the sealing station 104, do not facilitate/permit the intermittent pausing of an envelope at any desired location but require that a mailpiece 110 be (i) positioned in advance of the station, i.e., in queue awaiting the processing of other downstream stations, or (ii) fully processed by the station. For example, it can be detrimental to the sealing operation for a moistening applicator or nozzle 104A (best seen in FIG. 1b) to sit idly upon the flap (not shown) of the mailpieces 110. Hence, the transport of mailpieces 110 along the processing path PPH must be controlled to await the completion of the weighing operation before initiating the sealing operation, i.e., at the sealing station 104.
Additionally, while it can be desirable to combine structural elements of a mailing machine to (i) perform dual functions and (ii) reduce the number of parts to assemble/maintain, these seemingly synergistic structural combinations can further limit processing throughput. This is especially true in connection with the use of conveyor belts and rollers to transport mailpieces 110 along the processing path PPH. For example, in FIG. 1a, a single upper belt 112 spans the decks 106D, 108D of the weighing and print stations 106, 108 to transport mailpieces 110 across both stations 106, 108. While the single belt 112 provides the motive force for transporting the mailpieces 110 across both stations 106, 108 (i.e., saving component, assembly and maintenance costs), the transport functions of both are integrally connected irrespective the processing speeds attainable by one or the other of the stations 106, 108. That is, an upstream mailpiece 110A cannot be weighed by the weigh station 106 until processing of the downstream mailpiece 110B is completed by the printing station 108, and vice versa.
Finally, it will be appreciated that, in addition to the deck 106D of the weighing station 106 spanning a length sufficient to accommodate various mailpiece configurations, the deck 106D also spans the length of the print station 108. As such, a single structural platform is fabricated/machined to decrease manufacturing costs. While this adaptation may enable closer mailpiece spacing, it has the effect of decreasing throughput by increasing the time required to weigh a mailpiece. More specifically, the time required to weigh a mailpiece 110 is a function of the “settling time”, or the time required for the station deck 106D to dampen oscillations induced by the introduction of a mailpiece 110. That is, an accurate reading of weight can only be obtained when oscillations induced by the mailpiece 110 (i.e., each time a mailpiece is loaded and removed from the deck 110D) is damped below a threshold value (i.e., amplitude).
Inasmuch as the amplitude of weigh station oscillations is a function of the total mass of the spring/mass system (i.e., including, inter alia, the mailpiece 110, the deck 106D, rollers 106R and the upper belt 112), any additional or unnecessary mass will prolong the settling time, and, consequently, the time required to achieve an accurate weight measurement. Therefore, adaptations made to the weigh station 106 to incorporate a single elongated belt 112 or deck 106D can adversely impact the time to weigh a mailpiece 110, in addition to the processing throughput of the mailing machine 100.
A need, therefore, exists for a weight system or mailing machine having an improved weighing system or module which increases throughput without altering the operating speed or function of systems/modules upstream or downstream of the weighing module.